问题：使用非root账户tomcat启动tomcat报错：
19-Sep-2016 15:08:27.168 INFO [main] org.apache.coyote.AbstractProtocol.init Initializing ProtocolHandler ["http-nio-80"]
19-Sep-2016 15:08:27.179 SEVERE [main] org.apache.coyote.AbstractProtocol.init Failed to initialize end point associated with ProtocolHandler ["http-nio-80"]
java.net.SocketException: Permission denied
at sun.nio.ch.Net.bind0(Native Method)
at sun.nio.ch.Net.bind(Net.java:433)
at sun.nio.ch.Net.bind(Net.java:425)
at sun.nio.ch.ServerSocketChannelImpl.bind(ServerSocketChannelImpl.java:223)
at sun.nio.ch.ServerSocketAdaptor.bind(ServerSocketAdaptor.java:74)
at org.apache.tomcat.util.net.NioEndpoint.bind(NioEndpoint.java:339)
at org.apache.tomcat.util.net.AbstractEndpoint.init(AbstractEndpoint.java:737)
at org.apache.coyote.AbstractProtocol.init(AbstractProtocol.java:457)
at org.apache.coyote.http11.AbstractHttp11JsseProtocol.init(AbstractHttp11JsseProtocol.java:120)
at org.apache.catalina.connector.Connector.initInternal(Connector.java:960)
at org.apache.catalina.util.LifecycleBase.init(LifecycleBase.java:102)
at org.apache.catalina.core.StandardService.initInternal(StandardService.java:567)
at org.apache.catalina.util.LifecycleBase.init(LifecycleBase.java:102)
at org.apache.catalina.core.StandardServer.initInternal(StandardServer.java:851)
at org.apache.catalina.util.LifecycleBase.init(LifecycleBase.java:102)
at org.apache.catalina.startup.Catalina.load(Catalina.java:576)
at org.apache.catalina.startup.Catalina.load(Catalina.java:599)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.apache.catalina.startup.Bootstrap.load(Bootstrap.java:310)
at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:484)
19-Sep-2016 15:08:27.180 SEVERE [main] org.apache.catalina.core.StandardService.initInternal Failed to initialize connector [Connector[HTTP/1.1-80]]
org.apache.catalina.LifecycleException: Failed to initialize component [Connector[HTTP/1.1-80]]
at org.apache.catalina.util.LifecycleBase.init(LifecycleBase.java:106)
at org.apache.catalina.core.StandardService.initInternal(StandardService.java:567)
at org.apache.catalina.util.LifecycleBase.init(LifecycleBase.java:102)
at org.apache.catalina.core.StandardServer.initInternal(StandardServer.java:851)
at org.apache.catalina.util.LifecycleBase.init(LifecycleBase.java:102)
at org.apache.catalina.startup.Catalina.load(Catalina.java:576)
at org.apache.catalina.startup.Catalina.load(Catalina.java:599)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.apache.catalina.startup.Bootstrap.load(Bootstrap.java:310)
at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:484)
Caused by: org.apache.catalina.LifecycleException: Protocol handler initialization failed
at org.apache.catalina.connector.Connector.initInternal(Connector.java:962)
at org.apache.catalina.util.LifecycleBase.init(LifecycleBase.java:102)
... 12 more
Caused by: java.net.SocketException: Permission denied
at sun.nio.ch.Net.bind0(Native Method)
at sun.nio.ch.Net.bind(Net.java:433)
at sun.nio.ch.Net.bind(Net.java:425)
at sun.nio.ch.ServerSocketChannelImpl.bind(ServerSocketChannelImpl.java:223)
at sun.nio.ch.ServerSocketAdaptor.bind(ServerSocketAdaptor.java:74)
at org.apache.tomcat.util.net.NioEndpoint.bind(NioEndpoint.java:339)
at org.apache.tomcat.util.net.AbstractEndpoint.init(AbstractEndpoint.java:737)
at org.apache.coyote.AbstractProtocol.init(AbstractProtocol.java:457)
at org.apache.coyote.http11.AbstractHttp11JsseProtocol.init(AbstractHttp11JsseProtocol.java:120)
at org.apache.catalina.connector.Connector.initInternal(Connector.java:960)
... 13 more
问题分析：在centos上只有root用户才可以使用1024以下的端口号，其余用户不能
2.解决方案
方法①修改Tomcat的server.xml配置文件，将端口修改为8081（或者其他1024以上的端口号，不能与本机上的其它Tomcat端口冲突）
vim /usr/local/apache-tomcat-8.0.52/conf/server.xml
<Connector port="8081" protocol="HTTP/1.1"
connectionTimeout="30000"
maxThreads="2000"
acceptCount="2000"
URIEncoding="UTF-8"
redirectPort="9143" />
<!-- A "Connector" using the shared thread pool-->
方法②修改端口后，使用root用户登录服务器，执行端口重定向命令：iptables -t nat -A PREROUTING -p tcp –dport 80 -j REDIRECT –to-port 8081
意思就是当访问80端口时重定向到8081端口，这样，我们可以改成任何我们需要的端口啦。
iptables -t nat -A PREROUTING -p tcp --dport 80 -j REDIRECT --to-port 8081
切换到tomcat账号，启动tomcat服务